I

The protagonist of the books. The story in each book is told from his perspective. He is a second year student in a Japanese high school (equivalent to 11th grade in the US school system). His name is not given throughout the series. During middle school, he spent his time after school working on mathematics in the library. He begins to repeat this pattern in high school, but as his friendship with Miruka and Tetra develop he spends most of his time working on math problems with them. Other than the fact that he wears glasses, his physical characteristics are not described. He has a quiet personality, but is somewhat self-conscious of his mathematical ability as compared to Miruka and Tetra, and when he has difficulty solving a math problem he tends to become depressed. He is very conscious of Miruka and Tetra as potential love interests, but is too shy to initiate a relationship with either one. He acts as both a teacher and a student, at times working on problems given to him by Miruka or Mr. Muraki, at other times teaching Tetra. He does not like to speak before large groups of people, but he is not hesitant to speak up when teaching Tetra and Miruka.